Thin film capacitors have been under investigation for a long time for the purpose of suppressing a leakage current. For example, a thin film capacitor having a two-layer dielectric thin film formed of a first dielectric layer and a second dielectric layer and a pair of electrodes between which the two layers of the dielectric thin film are interposed and which face each other in parallel is disclosed in Japanese Unexamined Patent Publication No. 2010-232329. In this thin film capacitor, a leakage current is suppressed by numerous voids formed in an interface between the first dielectric layer and the second dielectric layer.
For example, a method of improving a leakage current characteristic of a dielectric the film by doping a composition for forming the dielectric thin film of a thin film capacitor or the like with aluminum (Al) is disclosed in Japanese Unexamined Patent Publication No. 2014-144881.
However, in the thin film capacitor disclosed in Japanese Unexamined Patent Publication No. 2010-232329, since the dielectric layer (the dielectric thin film) is formed of the plurality of layers, a thickness of the dielectric layer is easily increased. For this reason, it is difficult to improve capacitance of the thin film capacitor. Further, in the method of Japanese Unexamined Patent Publication No. 2014-144881, it is difficult to adjust an amount of aluminum (Al) with which the dielectric layer is doped, and to make the dielectric layer thin as well. Therefore, a thin film capacitor capable of suppressing the leakage current while keeping the dielectric layer thin is required.
The present invention was made in view of the above circumstances, and an object thereof is to provide a thin film capacitor capable of suppressing a leakage current while keeping a dielectric layer thin